Mechanisms for the precision movement and positioning of planar substrates over a substantially planar region may be used in semiconductor manufacturing equipment such as optical lithography, inspection and wafer probing tools. Similar devices may be found in other industries such as read-head manufacturing for the disk drive industry, flat-panel display manufacturing, printed circuit board manufacturing and gene-chip array imaging and analysis.
The semiconductor field presents an interesting example of the challenges that must be met by a substrate positioning system. With each generation of semiconductor device, the precision requirements of the tools used to manufacture the device increase. At the same time, there is a trend to ever larger substrate sizes. Over the previous thirty years of semiconductor manufacturing, substrate sizes have grown from 75 mm diameter to 300 mm diameter. At the same time, the critical dimensions of features on the wafer have decreased from ten microns to 0.1 micron.
One known stage mechanism for controlling planar motion is the H-stage, an example of which is shown in FIG. 1. The H-stage uses three linear motors to control two degrees of freedom. Dual Y motors 21a, 21b drive either ends of an X motor 22. A wafer stage 23 is driven by the X motor 22. A wafer stage 23 slides over a planar base 20. In some cases, a small amount of yaw motion may be controlled by driving the two Y motors 21a, 21b to slightly different dimensions; however, it may be difficult to achieve more than a few milliradians of yaw motion without adding a separate rotary stage 24 on top of the XY carriage. Further, in the H-stage, the X motor 22 dissipates heat directly under the wafer stage 23, which may lead to thermally-induced errors. Additionally, the Y motors 21a, 21b drive an increased mass that includes not only the wafer stage 23 but also the X-axis motor stators that may be made primarily of steel.
The following U.S. patents disclose systems for the manipulation of a substrate over a substantially planar region and are all incorporated herein by reference:
U.S. Pat. No. 4,654,571 to Hinds discloses a planar mechanism including drive coils that are carried by a moving member.
U.S. Pat. No. 4,891,526 to Reeds discloses a device that mounts an XY stage driven by links of varying length on top of a rotary stage.
U.S. Pat. No. 5,140,242 to Doran discloses a stage mechanism including drive links having controllable lengths to allow manipulation of a wafer. The drive links extend outward from the work envelope.
U.S. Pat. No. 6,324,933 to Waskiewicz discloses a stage including links of varying lengths extending outward from the work envelope to manipulate a wafer stage.
U.S. Pat. No. 6,144,118 to Cahill discloses a stage mechanism that incorporates active counterbalance masses to reduce disturbances caused by stage motions.
In addition, in “Optimal design of a flexure hinge based XYθ wafer stage”, Ryu et al describe a micromotion stage for manipulating wafers over a range of motion of less than 100 microns. The use of flexure hinges in the micromotion stage restricts the range of travel to less than 1 mm in X and Y and less than 1 degree in Theta (or “Yaw”).
The requirement to manufacture devices at ever more stringent precision requirements over larger substrate sizes has driven the requirements for stage mechanisms. Pressure to reduce manufacturing costs further aggravates the challenge of stage design for such equipment. Making equipment at lower cost and/or operating equipment at higher production speeds reduces manufacturing costs. However, achieving lower manufacturing costs while simultaneously increasing precision over a larger operating envelope presents a formidable set of requirements for a substrate manipulator.
Accordingly, it would be desirable to provide an economical mechanism that may operate over a substantially planar envelope at high throughput while achieving high-levels of precision. Furthermore, it would be desirable to manipulate a substrate over a range of motion comparable to the substrate size and to do so without shaking or tilting the stage that may be supported by a compliant vibration isolation system.